Flange rating

[rajat84]

Material SA 182 F 316L
Pressure temperature rating -2.2-3 (ASME B16.5 –Refrence)
Design temperature- 80
Design Pressure - 16 bar

As per ASME B16.5
Flange rating I cannot use class 150 as my pressure is above by 1 bar and if I use class 300 it is costly and has got very high rating than normal pressure required.

Please suggest – as material have already been brought in. Is it possible to use class 150 rating flanges for SA182 F 316L??

I did try to search on google but wasn't that helpful.

 

[TomBarsh]

Class 150 flanges, material 2.3, has pressure rating of 15.9 bar at ambient temperature, which is already below your design pressure (16.0 bar). At your design temperature the pressure rating will be even less.

Using the flange would not be permissible in ASME pressure vessel code. What Code are you designing to? If it adopts the ASME B16.5 standards then it is unlikely it will accept "over rating" the flanges either.

By using the flange at the higher pressure you would be reducing the safety factor. Is there additional hydrostatic head acting on the flange as well? Even though the design pressure is only slightly above the pressure rating are you willing to stake lives and your reputation on being the one to select the "cheaper" flange?

 

[doct9960]

rajat84,

Is your flange material dual certified 316/316L?

If YES, then you can use ASME B16.5 Table 2-2.2 for the P-T rating. Class 150 should be okay for the design conditions you mentioned. In the Manufacturer's Data Report, list SA-182 F316 as the flange material and in the "Remarks" section, indicate that the flange material meets all the requirements of SA-182 F316 and SA-182 F316L.

If NO, then you have no choice but to buy new sets of flanges that meets Code requirements.

The above is just my opinion. Ask your AI for his advice.

 

[rajat84]

Thanks guys-Your views are really helpful.

Yes I am designing as per ASME and cast analysis of the material is dual certified to ASME 182 F316L/ F316.

Just a hypothetical question- If the material was ordered in large amount and not dual certified,(i.e. only stated 316L)
A)Can I show them Flange calcs as per Appendix 2, if it comes out acceptable ?
B)I guess doing prodct analysis for proving material to be 316 will be out of question as cast analysis states 316L.

I will ask AI by thursday as he is in on that day

 

[TomBarsh]

"A": Yes, you could analyze the flange per Appendix 2. However, there is no assurance that standard ASME B16.5/B16.47 flange will meet their pressure-temperature rating when analyzed by Appendix 2. Some will meet, others will show as overstressed.

In general, "stocky" flanges (say, 6" class 600) will have a calculated MAWP by Appendix 2 that far exceeds the B16.5 rating. But a 24" class 150 will likely be highly overstressed when analyzed by Appendix 2.

Search eng-tips for related discussions as to how/why.